This server has many names, so an ordinary certificate with only one name will not work. A wildcard certificate can be used for situations like this, or when you have too many server names to make it practical to issue a certificate for each server. In some protocols, like the SIP protocol, wildcard certificates are not allowed.

Check that your client can successfully connect to both of these URLs, that lead to the same server with the same certificate.

Fork us on Github

All the tests, including keys and certificates, are available on Github.
https://github.com/edvinanet/tls-o-matic
That's also where you will find all the current tests while waiting for us to write documentation here.

What is TLS?

"The TLS protocol provides communications security
over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery."
From RFC 5446 that defines the current TLS - version 1.2. Wikipedia is also a good help in explaining TLS.